I've got two:
SEA-TPE: Sure, CI is present and a great SkyTeam option out of YVR/LAX, but it would be nice to not have to take a domestic connection to get to Taiwan. And while the KE deal makes it pretty unlikely, I'd love to see the ability to connect onward from TPE on CI to destinations that make sense (Australia, southeast Asia). I'd settle for CI starting SEA-TPE, though...
YVR-LAX: Because I have no intention of flying WestJet.